Merge branch 'drm-nouveau-fixes-3.8' of git://anongit.freedesktop.org/git/nouveau...

[deliverable/linux.git] / Documentation / devicetree / bindings / gpio / gpio-poweroff.txt

diff --git a/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt b/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
index 558cdf3c9abc8e10539c894a4387fc72c1b32ff3..d4eab9227ea4451bb0eefbd511c22288d5fe336b 100644 (file)
--- a/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
@@ -1,4 +1,19 @@
-GPIO line that should be set high/low to power off a device
+Driver a GPIO line that can be used to turn the power off.
+
+The driver supports both level triggered and edge triggered power off.
+At driver load time, the driver will request the given gpio line and
+install a pm_power_off handler. If the optional properties 'input' is
+not found, the GPIO line will be driven in the inactive
+state. Otherwise its configured as an input.
+
+When the pm_power_off is called, the gpio is configured as an output,
+and drive active, so triggering a level triggered power off
+condition. This will also cause an inactive->active edge condition, so
+triggering positive edge triggered power off. After a delay of 100ms,
+the GPIO is set to inactive, thus causing an active->inactive edge,
+triggering negative edge triggered power off. After another 100ms
+delay the GPIO is driver active again. If the power is still on and
+the CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
 
 Required properties:
 - compatible : should be "gpio-poweroff".
@@ -13,10 +28,9 @@ Optional properties:
   property is not specified, the GPIO is initialized as an output in its
   inactive state.
 
-
 Examples:
 
 gpio-poweroff {
        compatible = "gpio-poweroff";
-       gpios = <&gpio 4 0>; /* GPIO 4 Active Low */
+       gpios = <&gpio 4 0>;
 };